Crankshafts each including crank journals, crank pins, and crank arms have been known. Each of the crank journals is supported by a cylinder block and one of bearing caps. Each of the crank pin support the large end part of a connecting rod composed of a connecting rod body and a connecting rod cap. Each of the crank arms connects one of the crank pins to associated ones of the crank journals. Such a crankshaft is disposed in an engine, while being supported by a rotary part support structure for rotatably supporting crank journals and crank pins.
Patent Document 1 describes a rotary part support structure including sliding bearings, a flywheel, a first weight, and a second weight. The sliding bearings are attached to a cylinder block, and rotatably and pivotably support crank journals. The flywheel is connected to an end of a crankshaft, which projects out of the cylinder block. The first weight is attached to the flywheel. The second weight is connected to the other end of the crankshaft inside the cylinder block. Each sliding bearing is composed of a combination of an upper member and a lower member and has a cylindrical shape as a whole. The sliding bearing closest to the flywheel has a crowned portion at the end of a sliding face, which is closer to the first weight. On this sliding face, the upper member slides on the lower member. The crowned portion is a surface inclined so that the diameter of the sliding face increases from the inside toward the outside of the crankshaft.